Jesus saith unto them, My meat is to do the will of him that sent me, and to finish his work. John 4:34
A key part of Jesus’ thought is that when he talks about food, he is usually talking about spirituality. You see this again in the Beatitudes in Matthew.
Blessed are they which do hunger and thirst after righteousness: for they shall be filled.
Once you get this link, it seems what Jesus is talking about in the following line of the Our Father is spiritual.
Give us this day our daily bread.
Indeed, this line seems to express a similar thought to the first quoted in John above (‘My meat is to do the will of him that sent me’), because Jesus precedes the talk here about bread with doing the will of God (‘Thy will be done, in earth as it is in heaven; Give us this day our daily bread’). One reasonable conclusion from combining this with the passage from John, therefore, is that Jesus is implying in the Our Father that when one becomes a spiritual master, daily bread and doing the will of God on a daily basis are closely connected. I.e., if you continually do the will of God, you will get lots of spiritual nourishment on a daily basis.
So, ‘food’ = ‘spiritual nourishment’ for Jesus in many cases. This leads us to a more contentious passage.
Verily, verily, I say unto you, He that believeth on me hath everlasting life. I am that bread of life. Your fathers did eat manna in the wilderness, and are dead. This is the bread which cometh down from heaven, that a man may eat thereof, and not die. I am the living bread which came down from heaven: if any man eat of this bread, he shall live for ever: and the bread that I will give is my flesh, which I will give for the life of the world.
The Jews therefore strove among themselves, saying, How can this man give us his flesh to eat? Then Jesus said unto them, Verily, verily, I say unto you, Except ye eat the flesh of the Son of man, and drink his blood, ye have no life in you. Whoso eateth my flesh, and drinketh my blood, hath eternal life; and I will raise him up at the last day. For my flesh is meat indeed, and my blood is drink indeed. He that eateth my flesh, and drinketh my blood, dwelleth in me, and I in him. As the living Father hath sent me, and I live by the Father: so he that eateth me, even he shall live by me. This is that bread which came down from heaven: not as your fathers did eat manna, and are dead: he that eateth of this bread shall live for ever. John 6:48-58
Some Catholics claim Jesus meant this literally – that we must literally eat his flesh and drink his blood to have salvation. They use this to justify the Eucharist. Some anti-Catholics claim a literal interpretation of this passage is disgusting, and therefore the Catholic interpretation is disgusting, and if Jesus meant that, the many in attendance who left would have been right to do so.
The point I want to make here is that neither the pro-Catholic or anti-Catholic positions outlined above are accurate, because the actual Catholic position isn’t that Jesus literally becomes the bread and wine, and therefore any anti-Catholic positions based on that have a mistaken premise.
Consider. If I say I am literally eating a hamburger, I don’t mean I am eating something that doesn’t look, smell, or taste like a hamburger, or have a hamburger’s chemical structure, but rather has a hamburger’s ‘essence’ or ‘substance’ as opposed to its ‘accidents’. That is not a way of speaking literally about eating something. Since what Catholics claim is exactly that they are eating Jesus’s substance as opposed to his accidents, they aren’t talking literally. They too are saying Jesus meant by eating his flesh and drinking his blood something spiritual, but they then tie this to a theology of Jesus’ substance and the Last Supper. This is to push the question of what exactly is being claimed back a step (what do we mean by Jesus’ substance?), but it is still a spiritual, non-literal understanding of eating and drinking something.